Search for: All records

Understanding metabolism in the pathogen Candida glabrata is key to identifying new targets for antifungals. The thiamine biosynthetic (THI) pathway is partially defective in C . glabrata , but the transcription factor Cg Pdc2 upregulates some thiamine biosynthetic and transport genes. One of these genes encodes a recently evolved thiamine pyrophosphatase ( CgPMU3 ) that is critical for accessing external thiamine. Here, we demonstrate that Cg Pdc2 primarily regulates THI genes. In Saccharomyces cerevisiae , Pdc2 regulates both THI and pyruvate decarboxylase (PDC) genes, with PDC proteins being a major thiamine sink. Deletion of PDC2 is lethal in S . cerevisiae in standard growth conditions, but not in C . glabrata . We uncover cryptic cis elements in C . glabrata PDC promoters that still allow for regulation by Sc Pdc2, even when that regulation is not apparent in C . glabrata . C . glabrata lacks Thi2, and it is likely that inclusion of Thi2 into transcriptional regulation in S . cerevisiae allows for a more complex regulation pattern and regulation of THI and PDC genes. We present evidence that Pdc2 functions independent of Thi2 and Thi3 in both species. The C-terminal activation domain of Pdc2 is intrinsically disordered and critical for species differences. Truncation of the disordered domains leads to a gradual loss of activity. Through a series of cross species complementation assays of transcription, we suggest that there are multiple Pdc2-containing complexes, and C . glabrata appears to have the simplest requirement set for THI genes, except for CgPMU3 . CgPMU3 has different cis requirements, but still requires Pdc2 and Thi3 to be upregulated by thiamine starvation. We identify the minimal region sufficient for thiamine regulation in CgTHI20 , CgPMU3 , and ScPDC5 promoters. Defining the cis and trans requirements for THI promoters should lead to an understanding of how to interrupt their upregulation and provide targets in metabolism for antifungals.